It is often desirable to measure stresses and strains caused by loads or loading which occur in the use of prosthetic limbs. It may also be desirable to measure the inclination and acceleration of the prosthesis which are also critical to promote better gait. Such measurement may be made in connection with the design of prosthetic limb systems or with the fitting or adjustment of limbs, or the analysis of the user's motion in the course of operating a limb, as for example in the case of gait analysis. In other instances, loads may be measured or detected as part of an alarm system which indicates malfunction in a prosthetic limb. In yet other instances, such measurements may be used to control the operation of a component of a limb such as a motion damper, an electronically controllable joint, or other such structure.
In response to needs and applications such as the aforedescribed, the prior art has implemented various approaches to systems for measuring loads in prosthetic limbs. Some measurement systems rely upon the use of devices external to the limbs such as pressure plates and the like. Such systems are often difficult to use, and can interfere with a normal range of motion by the user; furthermore, such systems generally provide relatively limited data. Various onboard systems have been implemented; however, such systems generally require significant modification of a prosthetic limb. Hence they are not readily utilizable in connection with diagnosis of persons using preexisting limb systems. Furthermore, their complexity generally restricts their use to dedicated research applications.